Note the fuzzy glow surrounding Venus and the crescent. Those are faint coronas caused by water droplets in the atmosphere. The physics is basically the same as in the solar corona discussed below (see "Tree Rings").

The colorful rings or "corona" are caused by tiny droplets of water in clouds. Sunlight is diffracted from the surfaces of the droplets, producing a colorful interference pattern around the Sun. Curiously, there is no need for the droplets to be either spherical, transparent or even made of water. Small ice crystals, pollen grains and large dust particles all form coronas.

Potentially Hazardous Asteroids (PHAs) are space rocks larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones all the time.

Notes: LD is a "Lunar Distance." 1 LD = 384,401 km, the distance between Earth and the Moon. 1 LD also equals 0.00256 AU. MAG is the visual magnitude of the asteroid on the date of closest approach.

Essential Web Links

NOAA Space Environment Center -- The official U.S. government bureau for real-time monitoring of solar and geophysical events, research in solar-terrestrial physics, and forecasting solar and geophysical disturbances.

Atmospheric Optics -- the first place to look for information about sundogs, pillars, rainbows and related phenomena.